Disappointing Relationship between Functional Performance and Patient Satisfaction of UKA Patients: A Cross Sectional Study

Background: Following a Unicompartmental knee arthroplasty (UKA) satisfaction is often conflated with functional outcome. Recent studies have shown that satisfaction is not linked to functional outcome. The research questions were: (1) what is the relationship between satisfaction and functional performance and quality of life (absolute and gain values) after UKA? And (2) what is the level of satisfaction, function, and quality of life after UKA? Hypothesis: There is a poor relationship between functional performance and patient satisfaction following UKA. Methods: This was a retrospective study using a locally held arthroplasty register to identify patients who had undergone UKA between 2004 and 2017. Patient reported outcome measures (PROMs) were collected prospectively and included EQ-5D, Oxford Knee Score (OKS) and satisfaction score (based on a visual analogue score with 0 being worst and 100 being best). Patients with a complete set of pre-operative and 2-year post-operative outcome scores were included. Patients who subsequently underwent revision surgery were excluded. 1638 patients were identified, of which 896 were eligible for inclusion. The average age was 66.7 years old, with 46.3% of patients being female. Results: There was a moderate to strong correlation between the absolute or relative values for OKS and the patient satisfaction following UKA (r = 0.705 and r = 0.522, respectively). The average pre-operative scores improved from a median of 23 (IQR 18-28) to 43 (IQR 35-46) (p < 0.001) and from a median of 0.62 (IQR 0.186-0.691) to 0.85 (IQR 0.691 -1) (p < 0.001) for OKS and EQ-5D, respectively. In terms of satisfaction with outcome, 82.6% of patients were very satisfied and 4.4% were dissatisfied (scoring >= 80% and < 50%, respectively). At 2 years, the PASS was met or surpassed by 73.1% and 54.9% (OKS and EQ-5D, respectively). The MCID was met or surpassed by 93% and 78% (OKS and EQ-5D, respectively). Discussion/Conclusion: UKA is a successful procedure generating high levels of patient function and satisfaction. Because patients' OKS and EQ-5D scores may be influenced by comorbidities, those scores are of disappointing predictive value in estimating patient satisfaction, and therefore should not be used as a surrogate to determine the success of the UKA procedure. Level of Evidence: III; Restrospective cohort study. (c) 2021 Elsevier Masson SAS. All rights reserved.